While general proteins, nucleic acids in therapeutic or diagnostic use do not penetrate the cell membrane, it has recently been found that there are peptides that transport proteins, nucleic acids into cells and nuclei in living organisms (hereinafter also referred to as “TAT proteins”) (non-patent document 1 to non-patent document 3). Furthermore, it has been found that a fusion protein of a peptide consisting of 11 particular amino acids of the TAT proteins with another protein penetrates the cell membrane; such regions essential for cell membrane passage, i.e., cell penetrating peptides, are called PTDs (Protein Transduction Domains) (non-patent document 4).
To date, methods have been developed for transporting proteins, nucleic acids into cells by means of various cell penetrating peptides. Specifically, a method utilizing a particular partial polypeptide of the HIV-1 TAT protein (patent document 1) has been proposed.
However, cell penetrating peptides that have conventionally been used exist naturally, posing the problem of low translocation efficiency. For this reason, there has been a demand for the development of a peptide having a high transportation efficiency.
Patent document 1: JP-A-HEI-10-33186
Non-patent document 1: Green, M. et al. Cell 55, 1179-1188 (1988)
Non-patent document 2: Frankel, A. D. et al. Cell 55, 1189-1193 (1988)
Non-patent document 3: Fawell, S. et al. Proc. Natl. Acad. Sci. 91, 664-668 (1994)
Non-patent document 4: Nagahra, H. et al. Nature Medicine 4, 1449-1452 (1998)